Yi-Hsing Liu

ZnO-Based Ultraviolet Photodetectors With Novel Nanosheet Structures

This study presents the fabrication of ZnO nanosheets on a glass substrate using a room-temperature (approximately 25 °C) solution method. The average length and diameter of the ZnO nanosheets were 1.2 μm and approximately 5 nm, respectively. The ultraviolet (UV)-to-visible rejection ratio of the sample is approximately 42 when biased at 1 V, and the fabricated UV photodetector is visible-blind with a sharp cutoff at 370 nm. The transient time constants measured during the rise time and fall time were τr = 5.37 s and 6.02 s, respectively. The low-frequency noise spectra obtained from the UV photodetector were caused purely by the 1/ f noise. The noise-equivalent power and normalized detectivity ( D^*) of the ZnO nanosheet photodetector were 6.12 × 10 ^-9W and 2.17 × 10 ⁹ cm·Hz ^0.5 W ^-1, respectively.

Enhanced Field Emission Properties of Two-Dimensional ZnO Nanosheets Under UV illumination

In this paper, ZnO nanosheets were grown on glass substrates by using an aqueous solution at room temperature. It was found that the ZnO nanosheets were structurally uniform and well oriented with the wurtzite structure. The field emission performance of ZnO nanosheets can be greatly enhanced by illuminating UV light. It was found that the turn-on electric field can be reduced from 5.9 to 5.0 V/μm and field enhancement factors (β) can be increased from 1966 to 4202. It is attributed to generate a large number of electrons by UV illumination.

Ga-Doped ZnO Nanosheet Structure-Based Ultraviolet Photodetector by Low-Temperature Aqueous Solution Method

The fabrication of Ga-doped zinc oxide (GZO) nanosheets on a glass substrate was done using the aqueous solution method. A GZO nanosheet metal-semiconductor-metal ultraviolet (UV) photodetector (PD) was also fabricated. The average length and diameter of the GZO nanosheets were 1.28 μm and ~19 nm, respectively. The energy dispersive X-ray spectrum determined that the Ga-doped sample contains ~35% at.%. The UV-to-visible rejection ratio of the sample is ~36.1 when biased at 1 V, and the fabricated UV PD is visible-blind with a sharp cutoff at 370 nm. The photocurrent and dark-current constant ratio of the fabricated PD was ~14193 when biased at 1 V. The transient time constants measured during the rise time and the fall time were 2.45 and 4 s, respectively.

Ultraviolet Photodetectors With 2-D Indium-Doped ZnO Nanostructures

In this paper, we developed a simple method to fabricate an indium-doped ZnO nanostructure ultraviolet (UV) photodetector (PD) on a glass substrate. Through the aqueous chemical solution method, the indium-doped ZnO nanostructure uniformly grew on a glass substrate. The average length and diameter were 3.06 μm and 38 nm, respectively. At 1 V bias, the photo-to-dark current ratio of the indium-doped ZnO PD was 740 under UV light irradiation (365 nm). The sample exhibited fast response and recovery time. The increase and decrease times were 3.02 and 1.53 s, correspondingly. When irradiated at 360 nm, the UV-visible rejection ratio of the indium-doped ZnO nanostructure PD was approximately 312. The indium-doped ZnO nanostructure PD exhibited high sensitivity, fast response and recovery times, and good orientation properties.

UV Enhanced Field Emission Properties of ZnO Nanosheets With Different NaOH Concentration

In this paper, vertical ZnO nanosheets are synthesized on Si substrate using a simple solution-based method at room temperature to realize a field emission device. The thin nanosheets that were perpendicular to the Si substrate surface were mutually interwoven into net and formed a continuous nanosheet film, with a unique surface morphology and a high surface-to-volume ratio. The improvement in the FE properties under UV illumination is attributed to the generation of a large number of excited electrons and the edge effect, and demonstrates that the presented route is a simple route for realizing field emission devices. This method has low cost and effectively improves the FE properties of the devices.

Enhanced Field Emission Properties of Ga-Doped ZnO Nanosheets by using an Aqueous Solution at Room Temperature

In this paper, gallium (Ga)-doped ZnO nanosheets were fabricated successfully on a glass substrate by using aqueous solution method. It was found that the GaZnO nanosheets grown at room temperature were structurally uniform and well oriented with pure wurtzite structure. The turn-on fields of ZnO and GaZnO nanosheets were 5.9 and 4.67 V/μm, and field enhancement factors (β) were 1966 and 4037, respectively. The results indicate that Ga-doped ZnO nanosheets exhibit enhanced field emission (FE) properties and are a promising candidate in future FE-based device applications.

High Response of Ultraviolet Photodetector Based on Al-Doped ZnO Nanosheet Structures

We demonstrated the fabrication of Al-doped ZnO (AZO) nanosheets on a glass substrate using the aqueous solution method. AZO nanosheets for a metal–semiconductor–metal ultraviolet (UV) photodetector (PD) were prepared. The average length and diameter of the AZO nanosheets were 1.44 μm and approximately 25 nm, respectively. The EDX spectrum of the Al-doped sample indicates that it contains approximately 0.64% at% Al. Our results show the high sensitivity of the UV PD, which reached 5.98 × 105. The measured transient response time and recovery time were 0.7 and 2.5 s, respectively.

UV Enhanced Field Emission Properties of Ga-Doped ZnO Nanosheets

High-density gallium (Ga)-doped ZnO nanosheets were fabricated successfully on a glass substrate by aqueous solution method. The diameter and length of the Ga-doped ZnO nanosheets were ~25 nm and 2.16 μm, respectively. In the dark, the turn-ON field of Ga-doped ZnO nanosheets was 4.67 V/μm, and the field enhancement factor (β) was 4037. Under UV illumination, the turn-ON field and field enhancement factor were 2.83 V/μm and 6616, respectively.

The study of ultraviolet photosensors with IZO nanosheets

We developed a simple method to fabricate indium (In)-doped ZnO nanosheets UV photodetector on the glass substrate. The average length and diameter were 3.06 μm and approximately 38 nm, respectively. The In-doped ZnO nanostructure concentration was 0.34 at.% by SEM-EDX analysis. The UV-to-visible rejection ratio of the sample is ~312 when biased at 1 V, and the fabricated UV PD is visible blind with a sharp cutoff at 360 nm. The photocurrent and dark-current constant ratio of the fabricated PD was ~740 when biased at 1 V.